The Moulting Stages of the Pea-Crab (Pinnotheres pisum)

Abstract

Pinnotheres pisum is a small crab with a carapace between about 2−1 and 18 mm. wide. The females are commonly found parasitic in the mussel, Mytilus edulis, though they have been recorded from other bivalves. The males are free-swimming and are comparatively rarely found in mussels. These small crabs are never abundant, and not more than one female has ever been found in a mussel.